In this essay, I will summarize and expound more on the “divisible parts problem” in materialism and why the concept of the soul (or ‘mental substance’) avoids this type of problem found in materialism. I will also briefly present the so-called “interaction problem” or objection to the soul and show that this is far from a conclusive argument and that the idea of the soul is, nonetheless, a rational account of human consciousness.
As I have said before, the idea that one has a soul dodges the messy “divisible parts problem” in materialism. To quickly recap the problem with emergentist materialism, if the bearer of awareness is a material object like the brain or the body then this problem immediately arises: how does consciousness relate to the parts and whole of that material object? Is every conceivable part or unit of the brain conscious? Or is consciousness only an overarching property of the whole brain or good portion of it while none of the smaller parts have consciousness? This is a difficult problem that puts the emergentist into a dilemma.
If the emergentist opts for the position that the “whole brain” is conscious but none of its smaller parts are conscious, say, the atoms of the brain, then how is it that all these permanently unconscious parts of the brain are going to contribute to a brain being conscious at all? It seems that, if at the bottom, there are no perceiving, thinking parts then the whole object is not going to be conscious whatsoever since the whole brain would be composed of nothing but unconscious parts. After all, no matter how one puts a set of unconscious Lego blocks together, no consciousness will arise from it. It would be like a case of adding up a tall column of zeros, and still getting only zero as an answer. In a similar manner, if all the atoms of the brain, regardless of configuration, are always unconscious then how would the brain ever produce consciousness?
On the other hand, the materialist can always opt for a panpsychist position. That proposition says no matter how one breaks down the parts of the brain (or body), there is always a conscious being. But if that is so, then how would all these conscious bits of material combine together to form unified states of consciousness? Either way, whether the position is that the whole brain is conscious but none of its minuscule parts are conscious, or that we have consciousness down to the quarks making up the human mind, we have a “combination problem” one way or another.
The panpsychist position is probably the best answer the materialist can offer to resolve the divisible parts problem. This is because it seems less difficult to reason that several parts which already have consciousness can combine together and form levels of greater thought, compared to the other alternative where we have to expect consciousness to arise from parts that are permanently unconscious. Nevertheless, panpsychism (the theory that everything is conscious at some basic level) does not seem to be very promising considering it’s quite mysterious how conscious bits of divisible matter are going to combine together and form greater levels of awareness and understanding (aka: a human personality).
Alternatively, by using Ockham’s Razor, it’s not even necessary to postulate countless bits of conscious matter that have to combine together to explain our mental states. We can just opt for a simpler explanation, like the mind being a unified substance in its own right, bearing the consciousness we are pondering. It is often said that the soul has no parts so a “divisible parts problem” does not even arise with a soul-bearing consciousness. Even in cases in which the soul is said to have “parts,” these descriptions don’t resemble anything like the parts of material objects.
Sometimes the soul is described as having different “parts” in terms of having different powers. For instance, in the Christian tradition, the soul is often said to have the powers of memory, understanding and free will. But then the term “parts” in reference to the soul in this context can only be metaphorical, not something that has a composite nature like a material object that gains or loses parts throughout time.
There are also a few philosophers that hold that the soul has “parts” in the sense that it has “temporal parts” and that the soul perdures throughout time. In such a case, one would be favoring the theory of perdurantism.
This is the idea that one’s complete person would consist in one’s full history of existence. That is to say that one has only a limited temporal part of one’s complete person at each moment in time. One can think of the perdurantist account of persistence like a song on the radio. One does not have the full-scale song at each moment in time; the complete song consists in all the moments it’s being played out. At each moment, one has only a temporal part or stage of the song, but not the complete musical piece. In a similar manner, the perdurantist sees the human person persisting in time like a song. One does not have the full-scale person at each moment in time; one has only a temporal ‘part’ of oneself at each moment in time. Nonetheless, all the moments of one’s existence constitutes the full person.
Perdurantism differs from the theory of endurantism which says, by contrast, that one has their complete person at each moment in time and that one remains the same person within time. Both endurantists and perdurantists agree that an individual is numerically a single person throughout time. But they differ in their interpretations of how an individual is “one person” throughout time. But even if we were to grant that the soul “perdures” through time and that the soul has “parts” in the sense of having temporal parts, there still would be no “divisible parts problem” that arises like it does for the materialist account of mind.
The soul, being conscious at any particular period of time, would simply be a temporal part or stage of that soul being conscious at that moment in time. It would still be unintelligible to ask whether a tiny “atom” or “particle” of the soul is conscious whenever one is conscious, even given a perdurantist account of the mind. The soul, being a spiritual substance of mind, would not have parts in the sense of being composed of different things or pieces that can be gained or lost throughout time. The spiritual mind would still be “uncuttable” so to speak. The soul would still maintain a very simplistic, indivisible nature even if we were to suppose that the soul persists in time as a kind of perduring entity.
A temporal part of the soul—if this model of persistence works—-would simply be just an indivisible unit or particular that bears consciousness at a particular moment in time. It is just that all these indivisible units or “temporal parts” or stages of the soul together would constitute the full-scale soul or person in time with a perdurantist model.
In other words, regardless whether the soul perdures through time, or endures through time, or doesn’t even remain numerically the same soul throughout time, there is no “divisible parts problem” in the question of consciousness of the human soul. Whenever one perceives a red apple, or thinks about Kansas City or dreams about mountains, it is simply the soul or mental substance that has those conscious states. It’s senseless to ask whether a tiny atom in my mind has a piece of my consciousness.
The idea of the ‘simplified’ soul also avoids another related problem in materialism known as the “binding problem.” If the conscious subject is material, then how does the brain or body unite all the features of our consciousness into one unified, coherent state of awareness? We notice that we are aware of many different things at once, like many colors, shapes, dimensions, odors, feelings etc. How would a divisible, composite material object be able to unite all these perceptions or qualia into a unified state of awareness? How could it do this without dividing all these features into separate spheres of perception? But with the understanding that the mind is a simplistic substance that bears our mental states, this problem can be easily avoided once again. The idea that the mind is a spiritual substance can explain why we experience all these perceptions or qualia in a unified conscious manner.
Besides, any philosophical position that considers the conscious-self to be material and something divisible is doomed to have other problems as well. The obvious one is this; how can there even be a conscious self in the first place? There’s even more problems concerning the existence of matter, such as the famous “paradox of infinite division” rooted in Zeno.
The paradox of infinite division is this: since a material object is divisible, it seems that there is no limit to how a material object can be divided. But if a material object is infinitely divisible then it must have an infinite number of parts. However, if an object has an infinite number of parts, then how could any material object occupy a finite amount of space? Or, another related version of that paradox states that if any given material objects is infinitely divisible, then how can it be a unified, particular being?
There are, of course, different answers to the paradox of division. Some philosophers like George Berkeley have argued that the paradox shows that matter does not really exist. Others think that there are solutions to this paradox while preserving the belief that matter exists. And some philosophers, like Leibniz, have simply defined all entities as unified, indivisible particulars or “monads” so as to avoid any kind of paradox relating to divisibility.
We will not go through all the possible answers to the paradox of infinite division here but I bring up the paradox briefly just to illustrate the fact that it’s not desirable to portray the mind as a divisible, material object. The view that the mind is an indivisible, immaterial and simplistic substance is the more reasonable alternative and it avoids all the paradoxes relating to divisibility and consciousness.
Of course, while there is a strong case for the existence of the soul, the idea is open to objections, like every position out there. Perhaps the most common objection to the existence of mental substance is the so-called “interaction problem.” If the mind is immaterial, then how can it causally interact with the body? How can a mind that has properties that are different from the body be able to causally interact with the body? This poses a good question for the substance dualist or a person that endorses the notion that mind and body are two substances that somehow interact or correlate with each other.
However, it’s important to note, that interactionist substance dualism like in Descartes and St. Augustine actually appeals to common sense in its interpretation that mind and body are two different particulars and that they seem to interact. Consciousness is clearly not the same thing as matter or physical beings by Leibniz’s Law of Indiscernibility.
And it seems to be a well-established truth that the body can affect consciousness and conversely, one’s consciousness can affect the body. For instance, a person can make the choice to drink beer and that conscious choice later affects the person’s body and the person feels tipsy. Likewise, plenty of alcohol in the body, in turn, can affect a person’s mood. So, the mind and body do appear to causally interact.
While the question of ‘how can two types of substances interact with each other’ may be a good puzzle for the dualist, it is however, a rather inconclusive objection to dualism and the existence of the soul. There are at least three problems with advancing the “interaction objection.”
First of all, the objection itself, even if valid, does not refute substance dualism per se. A person can be a substance dualist and still reject the notion that the mind and body “causally interact” with each other. A substance dualist, for instance, can be a parallelist and say that mind and body only appear to interact but they do not causally effect each other. All we really have, according to parallelism, are patterns on how the conscious soul and body will behave, so to speak. So, the “interaction objection” is powerless to non-interactionist forms of substance dualism. Parallelism might be (arguably) an ad hoc move for the substance dualist, but nonetheless, it’s a possible option that is not vulnerable to the “interaction objection.”
Secondly, there seems to be no clear evidence that shows that two types of being, one mental and the other physical, cannot causally interact. We live in a world with a variety of countless things with countless differences and they all seem to causally engage with each other just fine. A human being can interact with a cat though they are two different types of living creatures. The Sun pulls the Earth into orbit and yet they’re two different things. Cane sugar and alcohol can affect a person’s mood and help that person experience happy thoughts. But the happy thoughts are not the same thing as sugar and alcohol. What reason would there be to substantiate the claim that two substances of body and soul cannot causally interact?
Do we know all that is possible? Do we even fully understand how cause and effect works in the world? And why would the mind and body (being different entities) necessarily prevent them from interacting? Do differences among things necessarily prevent things from causally impacting each other? While it may be a bit of a mystery of how two different types of being may interact with each other, it is, however, a bigger mystery on how it would be impossible for different entities to interact.
It’s even more of a mystery whenever a physicalist asserts that the two substances of mind and body cannot interact when the physicalist denies the existence of the immaterial realm altogether. After all, he has nothing from experience on which to ground that assertion. As much as materialists like to believe that their views are based on science, their proposition that a spiritual self cannot interact with a body is not based on any empirical observation. That holds true even given the terms of materialism itself.
Finally, a person does not have to be a substance dualist to endorse the idea of the soul or ‘mental substance’. A person can be an idealist and embrace the idea of the soul and reject both dualism and materialism. In fact, with idealism, there is no interaction problem or puzzle – at least in the form that it apparently takes in substance dualism.
The idealist reduces material objects to ideas among minds and everything that exists is mental for the idealist. So, there’s no problem of how a mental substance interacts with a physical substance within idealism. The idealist simply melts away the interaction problem by favoring a monistic metaphysics that reduces everything to mental substances and their ideas and reduces all causality to mental causation. So, again, even if the interaction objection were a successful refutation of substance dualism, it would not be a proof that persons have no souls.
Besides, materialism has its own “interaction problems”, ones that are not just related to the ‘divisible parts’ problem. The main problem with just about any form of materialism is that it fails to account how the mind seems to affect the body. For example, the materialist might opt for physicalism and try to reduce all causality to physical causes in order to avoid any mental-to-physical or physical-to-mental causation. The general incentive behind a monistic metaphysics is to get rid of any dualistic causal interaction problem of mental (immaterial) beings interacting with physical beings. Idealists make this sort of move only when they seek to reduce everything to mental causality, unlike physicalists. However, by reducing all causality within the material realm, the physicalist creates a new interaction problem as some thinkers have pointed out.
Suppose a barefoot person steps on a tack and then feels some intense pain. He then takes the tack out and treats the foot. In this sort of experience, evidently electric-chemical currents travel from the foot into the brain and the person experiences pain and, as a result, he removes the tack and treats the injury. Now if one is a physicalist, only matter, physical energy, space and time exist. So, the physicalist can only account for the experience in terms of activity within the body and its surrounding environment.
However, a problem arises. The physicalist picture of the experience fails to explain how consciousness is involved in the event. Not only does the person have biological processes with the nerves giving a signal to the brain, but also the person has a subjective feeling of pain. And that pain seems to affect the behavior of the person. The physicalist position cannot explain, by its own terms, how the consciousness of pain is germane to a person expressing frustration and taking the tack off. After all, if the person had the same physical processes occur with his body, but had no pain from stepping onto the tack then the person would not have reacted in frustration.
Remember, the physicalist wants to say that only mind-independent, external matter-in-space-and-time exists. So, the behavior of the person saying “ouch” and removing the tack can only be explained in terms of matter-in-motion, according to physicalism. But the problem is that the behavior of the person reacting cannot be explained solely by material terms. In addition to biological processes, like the signal traveling to the brain, the person also has consciousness like the feeling of pain, which is, in part, responsible for the reaction of the individual. Because physicalism reduces all reality to matter and energy in motion, it fails to explain the pain, or how consciousness in certain instances is relevant in human behavior.
In other words, physicalism does not seem to explain why the pain is, at least in part, responsible for the person’s behavior. And yet commonsense and experience suggests that pain (or pleasure) in some instances does contribute to the behavior of a person.
So even a rigid materialist, physicalist account fails to free us from all “interaction problems” when it comes to the philosophy of mind. Physicalismhas its own “interaction problem” due to how it only accepts external, material entities and thus omits the role consciousness in human action.
Thus, there are over-weighing reasons to believe that human persons have souls. The concept of soul or mental substance has serious advantages over materialistic accounts of the mind, and the notion of the soul dodges the “divisible parts problem” and other related problems like the “binding problem.” On top of that, the “interaction objection” to the soul seems to be powerless. But even if the “interaction objection” were successful, still, there would be other options on how the soul might relate to the body other than what is described by interactionist substance-dualism.
Overall, I find the concept of soul or mental substance to be a competent and well supported account of human consciousness. And history.
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